No abstract

BACKGROUND Escherichia coli AFP111, a facultative anaerobic strain, shows a very low cell growth and succinic acid production rate in minimal medium during exclusively anaerobic fermentation. Therefore, atmospheric and room temperature plasma (ARTP) and adaptive laboratory evolution (ALE) strategies were adopted to improve cell growth and succinic acid production under anaerobic conditions. RESULTS A mutant, BER208, was obtained by ARTP and ALE used successively. When cultured in a 3 L stirred bioreactor, the specific growth rate of BER208 was increased 3.12‐fold compared with AFP111. Also, it consumed 40 g L−1 glucose and produced 27.9 g L−1 succinic acid with a glucose utilization rate of 0.54 g L−1 h−1 and succinic acid productivity of 0.38 g L−1 h−1, which were 3.7‐fold and 2.5‐fold higher than those of the original strain. Further investigation showed that the activities of glucokinase and phosphoenolpyruvate carboxykinase (PCK) were increased 3.3‐fold and 16‐fold in the mutant compared with the original strain. CONCLUSION The combined strategy of ARTP and ALE was an effective approach to obtain mutants with improved performance. © 2015 Society of Chemical Industry

No abstract

The responsive self-assembled structures of ion-pairing amphiphile molecules will provide good insights into various fields.

Two gas spargers, a novel membrane-tube sparger and a perforated plate sparger, were compared in terms of hydrodynamics and mass transfer (or oxygen transfer) performance in an internal-loop airlift bioreactor. The overall gas holdup ε T, downcomer liquid velocity V d, and volumetric mass transfer coefficient K L a were examined depending on superficial gas velocity U G increased in Newtonian and non-Newtonian fluids for the both spargers. Compared with the perforated plate sparger, the bioreactor with the membrane-tube sparger increased the values of ε T by 4.9-48.8% in air-water system when the U G was from 0.004 to 0.04 m/s, and by 65.1-512.6% in air-CMC solution system. The V d value for the membrane-tube sparger was improved by 40.0-86.3%. The value of K L a was increased by 52.8-84.4% in air-water system, and by 63.3-836.3% in air-CMC solution system. Empirical correlations of ε T, V d, and K L a were proposed, and well corresponding with the experimental data with the deviation of 10%.